Methods for applying elastic to clothing and similar articles are well known in the art. The elastic is normally in the form of a ribbon or tape and is used to provide snug fits around areas such as waist or leg openings. For many years this elastic was attached by hand sewing. With the advent of disposable one-time-use garments the labor cost of hand sewing became prohibitive and other means of application had to be sought. Several patents can be cited as exemplary of the development of the art up to the time of the present invention.
Goujon et al., U.S. Pat. No. 3,488,778, show a disposable panty in which the elastic is apparently applied by glue bonding, although no specific means of accomplishing this is shown.
Butter, U.S. Pat. No. 3,560,292, shows a similar garment in which the elastic is "spot-welded" to the base textile. Again, he does not disclose an apparatus for accomplishing this result at high speed.
Burger, in U.S. Pat. No. 3,663,962, teaches a method of continuously applying longitudinal strips of stretched elastic to a panty-type garment by sewing or adhesive bonding. He deals with the problem of keeping the elastic flat on the material by essentially freeing it in its stretched state during application. This process is further described in U.S. Pat. No. 3,694,815 to the same inventor.
Bourgeois, U.S. Pat. No. 3,828,367, uses an adhesive bonding system to place stretched elastic along the waistline and leg openings of disposable panties. The elastic is applied continuously and severed when each article is trimmed from the continuous sheet of nonwoven material. While this achieves the desired result at the waistline, it leaves a strip of tensioned elastic across the front and rear transverse margins of the crotch or gusset sections. These are areas where elastic is not desirable either from functional or wearer comfort standpoints.
Buell, U.S. Pat. No. 4,081,301, shows in detail a commercially practical system of applying elastic to the leg openings of disposable diapers. Buell has faced two vexiing problems. He has avoided the complexity of applying the elastic in a curvilinear fashion and has substituted a design which allows straight line application. He has also found one solution to the problems of selectively placing the elastic where it is functionally desirable without also having it in places where it is unwanted, such as in Bourgeois.
A diaper made by the Buell process is shown in his patent U.S. Pat. No. 3,860,003. Here the elastic is functional only around the lower two-thirds of the leg opening. This, of course, is the region where leakage is most likely to occur.
One commonn feature noted in all of these patents is that it is easier to apply the elastic in an uninterrupted linear manner. By uninterrupted is meant in a continuous strand for the full length of the individual article. As seen in Bourgeois this often puts elastic where it is not wanted. Buell deals with this by adhesively bonding the elastic only in the area in which it is functionally desired, even though the tensioned elastic applied is equivalent to the full article length. The elastic strands are severed when the individual diapers are cut from the continuous assembly. This causes each end to relax to the unstretched length. These ends remain present but they serve no useful purpose. However, they tend to be somewhat unsightly from the user standpoint and waste about 20 percent of the relatively expensive elastic ribbon.
It is thus clear the art has not developed fully satisfactory methods for applying tensioned elastic at high speed to specified areas of articles, where such areas are less than the full length or width of the article.